"I do think that the hyper-test public reaction to this was sensitized by 9/11, but the notion that this action carries on the work of ... terrorists makes no sense to me at all in terms of the pattern of action," says Jerrold Post, a former CIA profiler who is now a George Washington University professor.

It may be days, if not weeks, before a conclusive picture can be drawn of the men seized at a rest stop in western Maryland  John Allen Muhammad, a former Army combat support specialist, and John Lee Malvo, a teenager described by law enforcement sources as Mr. Muhammad's stepson.

But former neighbors, wives, and colleagues have begun providing some details about Muhammad's life, describing him as an outgoing person and unremarkable neighbor who nevertheless had at times seemed to demonstrate an unseemly desire to control other peoples' lives, as well as angry reactions in personal disputes.

It is clear, for example, that Muhammad converted to Islam several years ago, but just changed his last name from "Williams" to "Muhammad" last year. It also appears that he spent 15 years in the US military, including stops at Fort Lewis Wash., and Fort Ord, Calif., and service in the Gulf War.

Several people, including law enforcement officials, said that both Muhammad and his stepson were known to speak sympathetically about the 9/11 hijackers.

Ideology may have played a part in Muhammad's actions, but as yet there is no proof. Among crucial unanswered questions: Why did he leave the military after fifteen years, with twenty years' service and full pension rights in sight? What are his links, if any, to domestic paramilitary extremist groups?

"There are a lot of scattered, little ... pieces, but nothing really pulls them together yet," says Stanley Bedlington, a former senior analyst at the CIA's Counterterrorism Center.

John Allen Muhammad is described by his former business partner in Tacoma, Wash. as having strong Muslim beliefs. Felix Strozier, who operated a martial arts school with Mr. Muhammad several years ago, also told reporters that Muhammad had attended the "Million Man March." Minister Louis Farrakhan, leader of the Nation of Islam, who has a history of anti-Semitism, organized that event in 1995. (Some reports had Muhammad claiming to have been part of the security force for the event.)

Experts on rightwing extremism say there are - paradoxically - overlaps between black nationalism/radical Islam and white supremacist types in that both hate Jews and both hate the US government. Chip Berlet, an expert on rightwing extremists with Political Research Associates in Somerville, Mass., notes that "the US extreme right shares three ideological affinities with some Islamic clerical fascist movements such as the Taliban and the al Qaeda networks, and some Black nationalist groups."

Mr. Berlet says these include: "A hatred of Jews who are seen in the traditional anti-Semitic caricature of running the world through secret conspiracies. A hatred of the U.S. government, seen as not just a global bully but also controlled by Jews. A desire to overthrow existing governments and replace then with monocultural nation states built around the idea of supremacist racial nationalism or supremacist religious nationalism or both mixed together."

At this point in the investigation, there appears not to be any distinguishing connection between the sniper's shooting victims - other than the fact that most were around the nation's capital. But that in itself may have been enough for a hateful and perhaps mentally unbalanced person to associate them as "enemies."

"It may be like the John Salvi case (where abortion providers were attacked), where you had someone who was arguably mentally ill, but who picked the targets based on a recognizable political/theological outlook," Berlet told the Monitor. "The political/theological outlook sets the stage, but it is the mental illness that writes the script for turning to violence.

Not all mentally ill people turn to violence, and some violence is carried out by people not mentally ill, but sometimes this is the dynamic." Mr. Strozier says he had a falling out with Muhammad over borrowed money that was never returned. Strozier described Muhammad as "manipulative...he would do anything to get his way."

But some aspects of Muhammad's personal life indicated other possible motivations for murder. Married at least twice and the father of at least four children, Muhammad was considered overly controlling at times by family members. At one point his first wife  Carol Williams, who now lives in Baton Rouge, Louisiana  received a call from his second wife saying that Muhammad had "kidnapped" the children they had had together, according to published reports.

Williams also reportedly said that after converting to Islam, Muhammad tried to tell her what to feed her own children.

It is possible that Muhammad chose Washington for his killing spree because it is the seat of a national government against which he wished to strike.

It is also possible that he simply chose it because of convenience. He and his stepson have reportedly resided in the Washington suburb of Clinton, Md., off and on since as early as 1999.

One thing is sure: as a case of mass murder, the Washington snipers shootings fit no previous pattern of American crime.

From the age and race of the killers, to the timing, location, and possible motives of their acts, many aspects of the murders were unprecedented, say experts.

"This whole case has been very erratic from the beginning," says Tomas Guillen, a professor at the University of Seattle who works on communication between serial killers and law enforcement.

Since the shootings began on Oct. 2, the murdered "has gone from being called a spree killer [who shoots without a cooling-off period], a serial killer, and finally an abductor holding the city hostage for $10 million," he says.

But one aspect, perhaps, was not unprecedented. In the end, many serial killers are undone by their sense of self-importance, as was apparently the case with Muhammad.

It was a tip from Muhammad himself that led police to the rest stop outside Frederick, Maryland, after all. In a cryptic phone call with investigators he told them to check with "Montgomery" if they did not believe him to be genuine. Authorities finally linked this statement with an open murder case and liquor store robbery in Montgomery, Alabama, which provided a crucial fingerprint, which led them to the teen Malvo, and thence to his stepfather.

Brian Levin, director of the Center for Hate and Extremism at California State University at San Bernardino, says he doesn't believe that these suspects wanted to get caught. The clues that were left were part of the sniper's sociopathic desire to prove he was smarter than everyone else, he explains.

"I honestly think it was his way of saying, 'OK, I'll throw you a slow pitch and you'll still strike out.' It was part of his thing with power and control and authority. He was saying to the police, 'I'll give you a clue and you'll still miss it.' But they didn't."

Professor Levin says ego will often trip up criminals who might otherwise have gotten away, as hubris pushes them to do something that sends out a flag.

The Unabomber would probably not have gotten caught if he'd stayed quiet and not issued his manifesto; Timothy McVeigh drew attention to himself with a license plate that was falling off.

"This guy not only felt compelled to commit more murders, but also to taunt the police, and that turned out to be his downfall," says Levin.